Glycosylated amino compounds consist of sugar and amino compounds bonded by non-enzymatic covalent bonds, so that glycosylated amino compounds are also called "saccharic amino compounds." Glycosylated proteins are one group of such compounds, and are produced in the food industry or for medical applications. Recently, glycosylated proteins have been used as markers for clinical examinations, since, in the human body, the concentration of glycosylated protein depends on the concentration of sugar which existed together with protein for a certain period in the past. The period depends on the average life time of the protein.
For example, the concentration of glycosylated hemoglobin, which is produced by the reaction between blood glucose and blood hemoglobin, depends on the average concentration of blood glucose one or two months previously. Moreover, the concentration of glycosylated albumin, which is produced by the reaction between blood glucose and serum albumin, depends on the average concentration of blood glucose one or two weeks previously. Therefore, in order to determine the past value of blood sugar of diabetic patients, the concentrations of glycosylated hemoglobin and glycosylated albumin in the blood of the patients are measured.
In order to measure a glycosylated protein in the human body with a high accuracy, a glycosylated protein is needed as a standard sample for controlling the measurement accuracy. Therefore, in the blood sugar examination for diabetics, glycosylated hemoglobin and glycosylated albumin of optionally determined concentration are produced artificially and used as a standard sample.
As the general process for producing the glycosylated protein for controlling the measurement accuracy, sugar and protein are mixed and the mixture is reacted by incubation at approximately 37.degree. C. for about seven days (See processes described in, for example, Mark Rendell et al, J.Lab. Cli. Med. 105, 63-69 (1985); and E. Schleicher and O. H. Wieland, J. Cli. Chem. Cli. Biochem. 19, 81-87 (1981) etc).
However, the conventional process for producing a glycosylated protein needs a long incubation step of about seven days. In addition, if it takes a long time to produce the glycosylated protein, samples containing the protein might be putrefied. In order to prevent this, the conventional process generally includes a sterilization step, but this complicates the process. In addition, a long incubation period is liable to cause the denaturation of protein.